Heating mode using combustion exhaust heat of engine cooling water or the like cannot be performed in a automotive air conditioner applied to an electric vehicle (EV), a hybrid vehicle (such as HEV and PHEV) and the like. Exhaust heat from a drive motor, a battery, or the like as an alternative to the engine can be used. However, the amount of exhaust heat is small, and a heating system with only the exhaust heat as a heat source cannot be realized.
Particularly, the engine is terminated as much as possible in hybrid vehicles to save fuel. Moreover, the amount of exhaust heat is small even when exhaust heat from a drive motor, an inverter, a battery, or the like as an alternative to the engine is used. Therefore, the heating system using only the exhaust heat as the heat source cannot be realized. Meanwhile, although a heating system using an electric heater can be considered, the heating power consumption is large relative to the battery capacity. Therefore, there is a problem that the drive distance of the vehicle is significantly reduced.
An automotive air conditioner of a heat pump system including an electric compressor can be considered as an automotive air conditioner applied to an electric vehicle and the like. However, in a heat pump of a reverse system for switching a refrigerant circuit to operate a condenser as an evaporator and operate an evaporator as a condenser during heating, a heat exchanger and the like, such as piping, an evaporator, and a condenser, included in the refrigerant circuit need to be able to be shared under different pressure conditions of cooling mode and heating mode. The automotive air conditioner applied to a vehicle of an existing engine drive system needs to be significantly changed. Defrosting of frost formed on an external evaporator when the ambient temperature is low is a major problem.
Meanwhile, an automotive air conditioner illustrated in PTL 1 is known as an example of an automotive air conditioner that allows heat pump heating using an evaporator of an existing system as an internal evaporator arranged in an HVAC unit (Heating Ventilation and Air Conditioning Unit). A heating circuit is additionally installed, wherein an internal condenser is arranged on a downstream of an internal evaporator in an HVAC unit of an automotive air conditioner including an existing refrigerant cycle for cooling, the internal condenser is connected to a discharge circuit of a compressor, a three-way valve is arranged on an outlet side to connect a receiver, a refrigerant from the receiver through a subcooler and an expansion valve arranged on an upstream of the internal evaporator in the HVAC unit is guided to an external condenser that functions as an evaporator during heating, and the refrigerant is circulated to a suction side of the compressor from the outlet side.
An automotive air conditioner illustrated in PTL 2 is proposed as another example of the automotive air conditioner that enables the heat pump heating using the evaporator of the existing system as the internal evaporator arranged in the HVAC unit. An internal condenser is arranged on a downstream of an internal evaporator in an HVAC unit of an automotive air conditioner including an existing refrigerant cycle for cooling. The internal condenser is connected to a discharge circuit of a compressor, and a parallel circuit of a bypass circuit including a first electronic expansion valve and a first solenoid valve is connected to an outlet side. The bypass circuit including a second solenoid valve is connected to a second electronic expansion valve and the internal evaporator.